Is it possible to use both external power jack and USB port with Arduino?

Question

I have the Arduino UNO board and I want to know if it is possible to use both the USB connection (for exchanging data) and the external jack to power supply it.

I will use the following cable: http://ecx.images-amazon.com/images/I/41OMXaj5cPL.SY355.jpg with a AC-DC 5V adaptor in order to power supply the Arduino. However, I want to use also the USB connection in order to send some data from the computer.

Both will be connected at the same time.

In short, I want the Arduino to be able to run even if the computer is OFF and whenever I open the computer to send data to Arduino from USB connection.

Is this possible? Will the Arduino Uno board support it?

Answer 1

Yes. From the official Arduino website:

Power

The Arduino Uno can be powered via the USB connection or with an external power supply. The power source is selected automatically.

External DC power will override USB power if the Arduino detects it. [Source]

Answer 2

as other said, it is absolutely possible to have both usb and power jack plugged in.

but be aware that if you shut down your computer and turn it on after, when reading the usb port you'll restart the Arduino and might loose important data.

Answer 3

yeah both of them can be used. If you want to upload the code in arduino then simply use the usb cable otherwise keep it on adapter. it wont harm the device.

What I personally do is, I keep on plugging the adapter and remove the usb once I am done with uploading and then test it as normally the usb cable is quite small and I normally work on robots so I need long wires.

Answer 4

if you want just plugs it in, it's ok but Arduino board will chose one and usb has priority to other power source. ********* Very important :***** if you are controlling other circuits, that are connected to an external power supply, with your Arduino and connecting it to your PC's usb, Arduino will have potential difference and it will cause current flow that will damage your PC and Arduino board. if you want to do such thing, you have to shield your Arduino board from your other circuits that you want to control and they have external power source. this could happen with optocouplers for digital ports, non signal analog ports with shield relays, and complex analog circuits for analog signals